help: actually bother to clean up memory

Even though the goal is for this to be run with an arena allocator,
nothing is currently enforcing that, so we should try to keep tidy.
This still leaks memory like crazy without an arena allocator, though.

source/help.zig

@@ -196,22 +196,25 @@ pub fn HelpBuilder(comptime command: anytype) type {
 
         fn args_brief(self: @This()) ![]const u8 {
             var buf = std.ArrayList(u8).init(self.writebuffer.allocator);
+            defer buf.deinit();
+
             const writer = buf.writer();
 
             for (comptime help_info.arguments) |arg| {
                 try writer.writeAll(" ");
                 if (!arg.required) try writer.writeAll("[");
-                try writer.print("<{s}{s}>", .{ arg.name, if (arg.multi) " ..." else "" });
+                try writer.writeByte('<');
+                try writer.writeAll(arg.name);
+                if (arg.multi)
+                    try writer.print(" [{s} ...]", .{arg.name});
+                try writer.writeByte('>');
                 if (!arg.required) try writer.writeAll("]");
             }
 
             return buf.toOwnedSlice();
         }
 
-        fn subcommands_brief(
+        fn subcommands_brief(_: @This(), subcommands: parser.CommandMap) []const u8 {
-            _: @This(),
-            subcommands: parser.CommandMap,
-        ) []const u8 {
             return if (subcommands.count() > 0)
                 " <subcommand ...>"
             else
@@ -220,6 +223,7 @@ pub fn HelpBuilder(comptime command: anytype) type {
 
         fn describe_arguments(self: @This()) !OptionDescription {
             var pairs = std.ArrayList(AlignablePair).init(self.writebuffer.allocator);
+            defer pairs.deinit();
 
             var just: usize = 0;
             for (comptime help_info.arguments) |arg| {
@@ -241,6 +245,7 @@ pub fn HelpBuilder(comptime command: anytype) type {
 
         fn describe_options(self: @This()) !OptionDescription {
             var pairs = std.ArrayList(AlignablePair).init(self.writebuffer.allocator);
+            defer pairs.deinit();
 
             var just: usize = 0;
             for (comptime help_info.options) |opt| {
@@ -257,6 +262,7 @@ pub fn HelpBuilder(comptime command: anytype) type {
 
         fn describe_option(self: @This(), opt: OptHelp) !AlignablePair {
             var buffer = std.ArrayList(u8).init(self.writebuffer.allocator);
+            defer buffer.deinit();
             const writer = buffer.writer();
 
             if (comptime opt.short_truthy) |tag| {
@@ -317,6 +323,7 @@ pub fn HelpBuilder(comptime command: anytype) type {
 
         fn describe_env(self: @This()) !OptionDescription {
             var pairs = std.ArrayList(AlignablePair).init(self.writebuffer.allocator);
+            defer pairs.deinit();
 
             var just: usize = 0;
             for (comptime help_info.env_vars) |env| {
@@ -338,6 +345,7 @@ pub fn HelpBuilder(comptime command: anytype) type {
 
         fn describe_subcommands(self: @This(), subcommands: parser.CommandMap) !OptionDescription {
             var pairs = std.ArrayList(AlignablePair).init(self.writebuffer.allocator);
+            defer pairs.deinit();
 
             var just: usize = 0;
             var iter = subcommands.keyIterator();
@@ -395,6 +403,7 @@ const ArgHelp = struct {
 };
 
 pub fn opt_info(comptime command: anytype) CommandHelp {
+    // TODO: this could be runtime and it would be slightly simpler.
     comptime {
         var options: []const OptHelp = &[_]OptHelp{};
         var env_vars: []const EnvHelp = &[_]EnvHelp{};